I would have used the smoke. Let me explain.
Per definition in a game everything is gamey. You can play with every asset you have, most of the time you do to win. (In any case I still have to discover the co-operative game species yet in wargames!)
In order to make your gaming experience more fun, you will try to get closer to reality and you have to admit CM is inviting you to do so.
Now you can decide with an oppoenent that some weapons are badly modelled and should be banned as "gamey". If agreed, fine. Everything else is then NOT "gamey". After all it's war (or a game about war) and in war everything is allowed. In the game everything is allowed within the limits of the model.
If you want to be at ease, just think of your supposedly gamey tactics as an innovation.
A German Tiger was also perceived as gamey by US troops in WWII, however they had to live with it (inside their model).
Using smoke to protect your troops? As a commander I would use it, if no other option is left.
Knowing it's over in 5mins? Well that is a limitation of the model being used, but you can make yourself a reason for it: I know I will have reinforcements soon, I can leave the position now, I bet the enemy will withdraw if they cannot make it now, etc... That is just in your imagination.
If you don't like that aspect look for solutions like banning or using a last turn randomiser. I read it exists for CMBO (PC -version).
Good gaming,